Water electrolysis system

ABSTRACT

A water electrolysis system includes a water electrolysis unit; a housing; a ventilation device configured to cause air to flow inside a space of the housing; and a heating device provided on an upstream side of a water electrolysis device in a flow path of the air. A control device controls operation of the ventilation device based on ventilation temperature information detected by a ventilation temperature sensor provided above the water electrolysis device. Furthermore, the control device controls operation of the heating device based on heating temperature information of a heating temperature sensor provided between the heating device and the water electrolysis device in the flow path.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-109234 filed on Jun. 7, 2018, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a water electrolysis system in which a water electrolysis unit is housed in a housing.

Description of the Related Art

Japanese Laid-Open Patent Publication No. 2016-056397 discloses a water electrolysis system that takes air (outside atmosphere) into a housing where a water electrolysis device is housed, to ventilate the inside of the housing. The air taken into the housing flows through the inside of the housing to remove hydrogen that has leaked out, and cools various devices provided inside the housing.

SUMMARY OF THE INVENTION

The water electrolysis system disclosed in Japanese Laid-Open Patent Publication No. 2016-056397 switches a fan, which is a ventilation device, between operating and non-operating, according to the hydrogen manufacturing state. Therefore, the water electrolysis system is affected by the temperature outside the housing, and the temperature inside the housing is prone to fluctuation.

For example, when the temperature is high in summer or the like, the water cannot be sufficiently cooled when the water electrolysis is being performed by the water electrolysis device, and consequently the devices inside the housing may operate in a state outside of a safe temperature range. On the other hand, when the temperature drops below the freezing point of water in the winter or the like, there is a concern that the water inside the water electrolysis unit will freeze.

The present invention takes the above situation into consideration, and it is an objective of the present invention to provide a water electrolysis system that can suitably adjust the temperature inside the housing even when the temperature outside the housing changes, to thereby maintain a favorable operating environment for each device.

In order to realize this objective, a water electrolysis system according to an aspect of the present invention includes a water electrolysis unit including a water electrolysis device configured to perform water electrolysis; a housing that includes therein a space through which air flows, and houses the water electrolysis unit in the space; a ventilation device configured to cause the air to flow inside the space; a heating device provided on an upstream side of the water electrolysis device in a flow path of the air, and configured to heat the air; a ventilation temperature sensor provided above the water electrolysis device in the space; a heating temperature sensor provided between the heating device and the water electrolysis device in the flow path; and a control device configured to control operation of the ventilation device based on ventilation temperature information detected by the ventilation temperature sensor, and also control operation of the heating device based on heating temperature information detected by the heating temperature sensor.

According to the present invention, by including the ventilation temperature sensor, the heating temperature sensor, and the control device, the water electrolysis system can appropriately control the operation of the ventilation device and the heating device. For example, since the temperature in the housing rises and hot air tends to gather in the top portion of the water electrolysis device during the summer, the control device can lower the temperature inside the housing by increasing the ventilation air flow rate based on the ventilation temperature information of the ventilation temperature sensor. Furthermore, even when the temperature outside the housing drops in winter, it is possible to avoid freezing of the water electrolysis unit by using the heating device to heat the air based on the heating temperature information of the heating temperature sensor provided in the flow path between the water electrolysis device and the heating device. In other words, the water electrolysis system can maintain a favorable operating environment for each device by suitably adjusting the temperature in the housing, even as the temperature outside the housing changes throughout the year.

The above and other objects features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view schematically showing a water electrolysis system according to an embodiment of the present invention;

FIG. 2 is a descriptive diagram for describing a water electrolysis unit of the water electrolysis system;

FIG. 3A is a front view showing a ventilation device in a state where the cutoff device is closed, and FIG. 3B is a front view showing the ventilation device in a state where the cutoff device is open;

FIG. 4 is a block diagram of a control device of the water electrolysis system;

FIG. 5 is a time chart showing ventilation control of the water electrolysis system; and

FIG. 6 is a time chart showing heating control of the water electrolysis system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes examples of preferred embodiments of the present invention, while referencing the accompanying drawings.

A water electrolysis system 10 according to an embodiment of the present invention is a stationary system installed in a hydrogen supplying facility or the like, and includes a water electrolysis unit 12 that manufactures hydrogen and oxygen by performing water electrolysis, as shown in FIG. 1. This water electrolysis system 10 is formed such that the majority (or the whole) of the structure of the water electrolysis unit 12 is housed inside a housing 14.

The housing 14 of the water electrolysis system 10 includes a space 14 a therein through which air flows. In addition to the water electrolysis unit 12, a ventilation device 16, a heating device 18, and a control device 20 are arranged inside the housing 14.

As shown in FIGS. 1 and 2, the water electrolysis unit 12 includes a water electrolysis device 22 (differential pressure water electrolysis device) that actually produces the hydrogen and the oxygen and a water circulation circuit section 24 that causes water to circulate to and from the water electrolysis device 22.

The water electrolysis device 22 of the water electrolysis unit 12 generates hydrogen (high-pressure hydrogen) with a pressure, e.g., 1 MPa to 70 MPa, that is higher than the normal pressure of oxygen. The water electrolysis device 22 may also be configured to generate hydrogen at normal pressure. For example, the water electrolysis device 22 is formed by stacking a plurality of water electrolysis cells 26, includes a first end plate 28 at one end in the stacking direction, and also includes a second end plate 30 at the other end in the stacking direction. An electrolysis power source 32, which is a DC (direct current) power source, is connected to the stacked body of the water electrolysis cells 26.

The first end plate 28 is provided with a water supply port 28 a, and the second end plate 30 is provided with a water discharge port 30 a and a hydrogen outlet port 30 b. One end of a high-pressure hydrogen pipe 34 is connected to the hydrogen outlet port 30 b. The water electrolysis device 22 outputs hydrogen to an adsorption device and a high-pressure hydrogen gas-liquid separation device (not shown in the drawings) that are connected to the other end of the high-pressure hydrogen pipe 34.

The high-pressure hydrogen gas-liquid separation device and the adsorption device are installed in an adjacent module (e.g., an adjacent housing not shown in the drawings) that is outside the housing 14. The high-pressure hydrogen gas-liquid separation device separates water from hydrogen, and the adsorption device adsorbs water included in the hydrogen to generate commercial hydrogen (dry hydrogen). The generated hydrogen is stored in a hydrogen tank (not shown in the drawings) provided outside the housing 14. The high-pressure hydrogen gas-liquid separation device, the adsorption device, the hydrogen tank, and the like may instead be provided inside the housing 14.

The water circulation circuit section 24 includes a water circulation pipe 36 that is connected to the water supply port 28 a and the water discharge port 30 a of the water electrolysis device 22. An oxygen gas-liquid separation device 38, a water circulation pump 40, and an ion exchange device 42 are provided on the water circulation pipe 36.

The water circulation pipe 36 supplies water from the oxygen gas-liquid separation device 38 to the water electrolysis device 22. Also, the water circulation pipe 36 supplies (discharges) the water used in the water electrolysis from the water electrolysis device 22 to the oxygen gas-liquid separation device 38.

The oxygen gas-liquid separation device 38 separates a gas (oxygen, hydrogen, or the like) from a liquid (water) discharged from the water electrolysis device 22. This oxygen gas-liquid separation device 38 is connected to an oxygen supply pipe 44, a pure water supply pipe 46, and an exhaust pipe 48, in addition to the water circulation pipe 36. A blower 50 that supplies air to the oxygen gas-liquid separation device 38 is connected to the oxygen supply pipe 44.

A pure water production device 52 that supplies pure water to the oxygen gas-liquid separation device 38 is connected to the pure water supply pipe 46. The pure water production device 52 includes an ion exchanging unit 52 a that has a cation exchange resin and an anion exchange resin, and removes chlorine and the like included in municipal water.

The exhaust pipe 48 discharges the gas (oxygen, hydrogen, and the like) separated from the water by the oxygen gas-liquid separation device 38, to the outside of the housing 14, due to the air supply from the blower 50. The oxygen gas-liquid separation device 38 causes the water separated from the gas to flow out to the water circulation pipe 36.

The water circulation pump 40 is installed on the water circulation pipe 36, downstream from the oxygen gas-liquid separation device 38. As an example, the water circulation pump 40 is a centrifugal pump having fins (not shown in the drawing) whose rotational speed can be set, and applies a flow force corresponding to the rotational speed of the fins to the water. In other words, water whose flow rate has been suitably adjusted based on the rotational speed of the water circulation pump 40, is circulated through the water circulation pipe 36.

The ion exchange device 42 is installed on the water circulation pipe 36, downstream from the water circulation pump 40. The ion exchange device 42 includes an ion exchanger such as an ion exchange resin therein, and removes impurities by causing an ion exchange effect with the ions contained in the water.

The housing 14 that houses the water electrolysis unit 12 described above has a sufficient amount of space remaining therein when the water electrolysis unit 12 is housed therein, as shown in FIG. 1. Specifically, the housing 14 includes a pedestal 54 on which the water electrolysis unit 12 is installed and secured and a case 56 that is connected to the pedestal 54 and shaped as a box with a height from the pedestal 54 that is sufficiently greater than the height of the water electrolysis unit 12. Furthermore, in the water electrolysis system 10 according to the present embodiment, a roof duct 58 is attached to the top portion of the housing 14 (case 56).

A frame 60 is connected and secured to the pedestal 54 of the housing 14, and the water electrolysis unit 12 is installed at a prescribed position inside the housing 14 via the frame 60. When assembled together with the pedestal 54, the case 56 forms the space 14 a into which air (outside atmosphere) can flow from outside of the housing 14. The case 56 includes a ventilation inlet 62 that allows air to flow into the space 14 a and a ventilation outlet 64 that allows air in the space 14 a to flow to the outside.

The ventilation inlet 62 is provided in one of four side walls 66 that form the case 56, and causes the space 14 a inside the housing 14 to be in communication with the outside of the housing 14. The ventilation device 16 is attached to this ventilation inlet 62. The ventilation device 16 operates to cause the air outside the housing 14 to flow into the space 14 a. The configuration of the ventilation device 16 is described in detail further below.

The ventilation outlet 64 is provided in a ceiling wall 68 forming the case 56. The ventilation outlet 64 is arranged at a position furthest from the side wall 66 provided with the ventilation inlet 62, and this position is set to be approximately directly above the water electrolysis device 22. By overlapping the ventilation outlet 64 with an opening in the roof duct 58, the space 14 a of the housing 14 and an internal space 58 a of the roof duct 58 are caused to be in communication with each other.

The roof duct 58 is configured to cover the entire ceiling wall 68 of the case 56, while including an internal space 58 a with a prescribed volume therein. The roof duct 58 blocks direct sunlight from hitting the housing 14 from above and also allows the air discharged from the ventilation outlet 64 to flow through the internal space 58 a, thereby enhancing the thermal insulation performance of the housing 14.

The roof duct 58 is configured, for example, to extend over an upper part of an adjacent housing of the adjacent module described above, and to cause the internal space 58 a of the roof duct 58 to be in communication with the adjacent housing. In other words, air that flows from the ventilation outlet 64 to the internal space 58 a is guided to the adjacent housing in which a hydrogen tank or the like is housed, to thereby perform ventilation of the adjacent housing, and the air is then discharged to the outside (in FIG. 1, the state of discharging the air from the internal space 58 a to the outside is shown by a dotted line for the sake of convenience).

Furthermore, an internal wall structure 72 that forms a flow path 70 for the air that has flowed into the space 14 a from the ventilation inlet 62 is provided inside the housing 14. Specifically, in the cross-sectional side view of FIG. 1, the internal wall structure 72 includes a first internal wall 72 a that is connected to a side wall 66, extends substantially vertically upward from a position somewhat distanced from the ventilation inlet 62, and then extends horizontally after reaching a prescribed top end position, and a second internal wall 72 b that extends vertically downward from the ceiling wall 68 at a position distanced from the first internal wall 72 a. The water electrolysis unit 12 (the majority of the structure and the water electrolysis device 22) is installed below and at the side of the internal wall structure 72 (i.e., outside the internal wall structure 72).

The ventilation device 16 provided at the ventilation inlet 62 includes a plurality (four in the present embodiment) of fans 74, as shown in FIGS. 3A and 3B. Specifically, in a case of a front view of the side wall 66 of the housing 14 where the ventilation device 16 is provided, first to fourth fans 74A to 74D are included in the stated order from left to right. Each of the first to fourth fans 74A to 74D is capable of rotating independently and includes the same propeller 75 and a rotational drive section (not shown in the drawings) such as the same motor and the like. Therefore, by supplying the same power amount to the first to fourth fans 74A to 74D under the control of the control device 20, the first to fourth fans 74A to 74D rotate at the same rotational speed as each other to thereby cause air to flow into the space 14 a.

Here, among the first to fourth fans 74A to 74D, the second and third fans 74B and 74C, which are provided in the center, are regular fans 76 that always rotate and cause air to flow while the water electrolysis unit 12 is being operated (or not operated). On the other hand, among the first to fourth fans 74A to 74D, the first and fourth fans 74A and 74D, which are at respective ends, are additional fans 78 that rotate as needed to increase the flow rate of the air. In other words, the control device 20 determines whether it is necessary to cool the inside of the housing 14, stops the rotation of the first and fourth fans 74A and 74D if cooling is not necessary, and causes the first and fourth fans 74A and 74D to rotate if cooling is necessary.

Furthermore, the ventilation device 16 includes a cutoff device 80 that cuts off the flow of air by setting the first and fourth fans 74A and 74D to be closed off from the outside of the housing 14, when rotation of the first and fourth fans 74A and 74D is stopped. For example, a louver including a plurality of wing plates 80 a provided rotatably and in parallel, upstream from the first and fourth fans 74A and 74D, can be used as the cutoff device 80. Under the control of the control device 20, the cutoff device 80 is switched between a closed state for the first and fourth fans 74A and 74D (air flow cutoff state) and an open state for the first and fourth fans 74A and 74D (air flow allowed state).

Returning to FIG. 1, the flow path 70 inside the housing 14 includes a regular flow path 70 a through which the air brought in by the regular fans 76 flows and an additional flow path 70 b through which the air brought in by the additional fans 78 flows.

The regular flow path 70 a is a path in which, based on the internal wall structure 72 in the housing 14, air is first directed upward, then turned back to travel horizontally downward along a protruding end of the first internal wall 72 a, and then directed further downward (bottom side of the protruding end of the second internal wall 72 b) to exit the internal wall structure 72. The water electrolysis system 10 includes the heating device 18 at a position in this regular flow path 70 a.

On the other hand, the additional flow path 70 b is a path in which the air brought in by the additional fans 78 does not pass through the heating device 18. For example, the additional flow path 70 b may be configured such that air is directed from the additional fans 78 to the control device 20 either directly or in a bypassing manner, and then is directed to the bottom side of the second internal wall 72 b to exit the internal wall structure 72, as shown by the dotted-line arrow in FIG. 1.

The water electrolysis system 10 includes, on the upstream side of the flow path 70, a filter 82 that removes foreign objects such as trash or dust contained in the air flowing into the space 14 a. This filter 82 is provided at a location in the regular flow path 70 a where the air is directed upward, a location in the additional flow path 70 b between the additional fans 78 and the control device 20, or the like.

The heating device 18 is attached near the top portion of the second internal wall 72 b in the internal wall structure 72. The heating device 18 includes a box 84 that covers the protruding end (the position where the air is folded back) of the first internal wall 72 a, from above and below, and a cavity 84 a through which the air can flow is formed within the box 84. By assembling the box 84 and the first internal wall 72 a together, the cavity 84 a forms a portion of the regular flow path 70 a through which the air flows.

A plurality of heating wires 86 for heating air that has flowed into the box are provided in the box 84. In other words, by supplying power to the heating wires 86, the heating device 18 heats the air that flows into the cavity 84 a and is turned back along the first internal wall 72 a, and supplies the warm air (heated air) to the downstream side from the heating device 18 in the regular flow path 70 a.

The control device 20 of the water electrolysis system 10 is installed on the lower side in the internal wall structure 72. As described above, the internal wall structure 72 is disposed above and to the side of the water electrolysis device 22 in the housing 14, and therefore the control device 20 is positioned upstream from and to the side of the water electrolysis device 22.

The control device 20 is configured as a computer (including a microcontroller) that has a processor, a memory, and an input/output interface (not shown in the drawings), and controls the operation of the entire water electrolysis system 10. For example, the control device 20 controls the power supply of the electrolysis power source 32 of the water electrolysis unit 12 and the operation of the water circulation pump 40, to thereby switch between implementation and non-implementation (standby) of the water electrolysis by the water electrolysis device 22.

The control device 20 controls the operation of the ventilation device 16 and the heating device 18 provided in the housing 14 of the water electrolysis system 10. In order to control the ventilation device 16 and the heating device 18, a plurality of temperature sensors that provide temperature information to the control device 20 and a flow rate sensor 92 that provides the flow rate of the air to the control device 20 are provided inside the housing 14.

A ventilation temperature sensor 88 and a heating temperature sensor 90 are provided as the plurality of temperature sensors. The ventilation temperature sensor 88 and the heating temperature sensor 90 are each provided at a suitable position inside the housing 14, and enable the ventilation device 16 and the heating device 18 to operate at suitable timings.

Specifically, the ventilation temperature sensor 88 is provided at a position near the ventilation outlet 64, i.e., above the water electrolysis device 22 in the housing 14. The ventilation temperature sensor 88 detects hot air in the space 14 a that has been heated by each device (the water electrolysis unit 12 and the like) of the water electrolysis system 10, and outputs ventilation temperature information to the control device 20 as temperature information.

On the other hand, the heating temperature sensor 90 is provided in the space 14 a (flow path 70) between the heating device 18 and the water electrolysis device 22 inside the housing 14. In the present embodiment, two heating temperature sensors 90 (referred to below respectively as the first heating temperature sensor 90 a and the second heating temperature sensor 90 b) are provided in the housing 14.

The first heating temperature sensor 90 a is provided at a position near the downstream side of the heating device 18, detects the temperature of the air flowing out from the heating device 18, and outputs first heating temperature information to the control device 20 as temperature information. The behavior (hot air temperature) of the heating device 18 can be favorably monitored by this first heating temperature sensor 90 a. Furthermore, the second heating temperature sensor 90 b is provided at a position near the upstream side of the water electrolysis device 22, detects the temperature of the air that has exited the internal wall structure 72 and is heading toward the water electrolysis device 22, and outputs second heating temperature information to the control device 20 as temperature information. By using this second heating temperature sensor 90 b, it is possible to restrict the occurrence of insufficient heating of the water electrolysis device 22.

The flow rate sensor 92 is provided inside the ventilation outlet 64 of the housing 14 (or at a position near the ventilation outlet 64). The flow rate sensor 92 detects the ventilation air flow rate, which is the flow rate of air flowing out from the ventilation outlet 64.

The control device 20 forms a ventilation control section 94 and a heating control section 96, as shown in FIG. 4, as function sections for controlling the ventilation device 16 and the heating device 18, by having a processor execute a program (not shown in the drawings) stored in a memory.

More specifically, a ventilation determining section 98, a flow rate calculating section 100, a ventilation content setting section 102, a regular fan command section 104, an additional fan command section 106, and a cutoff device command section 108 are formed within the ventilation control section 94. Furthermore, a heating determining section 110 and a heating device command section 112 are formed within the heating control section 96.

The ventilation determining section 98 acquires the ventilation temperature information detected by the ventilation temperature sensor 88, and makes a comparison between this ventilation temperature information and temperature threshold values held therein in advance. The ventilation determining section 98 includes, as the temperature threshold values, a flow rate increase starting threshold value FTs that is a prescribed temperature value, and a flow rate increase stopping threshold value FTe that is a temperature value lower than the flow rate increase starting threshold value FTs. While the additional fans 78 are rotationally stopped, the ventilation determining section 98 compares the ventilation temperature information to the flow rate increase starting threshold value FTs, and provides the result of the comparison to the ventilation content setting section 102. While the additional fans 78 are rotating, the ventilation determining section 98 compares the ventilation temperature information to the flow rate increase stopping threshold value FTe, and provides the result of this comparison to the ventilation content setting section 102.

The flow rate calculating section 100 acquires the flow rate information detected by the flow rate sensor 92, and calculates the flow rate of the air near the ventilation outlet 64. The flow rate sensor 92 detects the flow rate as an instantaneous value, and therefore outputs flow rate information that fluctuates by a small amount up and down (see FIGS. 5 and 6 as well). Therefore, the flow rate calculating section 100 calculates the moving average value in a range of 5 sec to 30 sec, for example, from the acquired flow rate information, and provides the ventilation content setting section 102 with a calculated flow rate value that changes smoothly on the time axis.

The ventilation content setting section 102 determines the control content of the ventilation device 16 (including the cutoff device 80), based on the comparison result of the ventilation determining section 98 and the calculated flow rate value of the flow rate calculating section 100.

Specifically, in a state where the ventilation temperature information is less than or equal to the flow rate increase starting threshold value FTs, the ventilation content setting section 102 implements normal ventilation control that causes the regular fans 76 to rotate and causes the additional fans 78 to stop rotating. When the ventilation temperature information changes from being less than or equal to the flow rate increase starting threshold value FTs and instead exceeds the flow rate increase starting threshold value FTs, the ventilation content setting section 102 implements forced air cooling control that causes the additional fans 78 to rotate. The specific control performed by the ventilation device 16 is described further below.

Furthermore, the ventilation content setting section 102 sets the rotational speed (number of revolutions per unit time) of the first to fourth fans 74A to 74D (see FIGS. 3A and 3B) during rotation, based on the calculated flow rate. In the water electrolysis system 10, since the hydrogen is produced by the water electrolysis unit 12, it is possible that hydrogen is present in the space 14 a of the housing 14. Therefore, feedback of the flow rate information of the flow rate sensor 92 is performed and the rotational speed of the first to fourth fans 74A to 74D is maintained to be greater than or equal to a prescribed rotational speed, in order to reliably discharge the hydrogen from the housing 14 and establish ventilation to prevent explosions. In the present embodiment, in both of a case where only the regular fans 76 are driven and a case where the additional fans 78 are also driven along with the regular fans 76, the first to fourth fans 74A to 74D are rotated with the same rotational speed as each other.

The regular fan command section 104 controls the operation of the regular fans 76 by outputting a regular fan command to a driver (not shown in the drawings) of the regular fans 76, according to the commands of the ventilation content setting section 102. The additional fan command section 106 controls the operation of the additional fans 78 by outputting an additional fan command to a driver (not shown in the drawings) of the additional fans 78, according to the commands of the ventilation content setting section 102. The drivers of the regular fans 76 and the additional fans 78 implement PID control to perform rotational driving in accordance with the target rotational speed. Furthermore, the cutoff device command section 108 controls the operation of the cutoff device 80 by outputting a cutoff device command to a driver (not shown in the drawings) of the cutoff device 80, according to the commands of the ventilation content setting section 102.

On the other hand, the heating determining section 110 of the heating control section 96 acquires the heating temperature information detected by the heating temperature sensor 90, and makes a comparison between this heating temperature information and threshold values held therein in advance. The heating determining section 110 includes, as the threshold values, a heating start threshold value HTs that is a prescribed temperature value, and a heating stop threshold value HTe that is a higher temperature value than the heating start threshold value HTs.

As described above, the water electrolysis system 10 includes the first heating temperature sensor 90 a and the second heating temperature sensor 90 b as heating temperature sensors 90. Therefore, a first heating start threshold value HTs1 for the comparison with the first heating temperature information of the first heating temperature sensor 90 a and a second heating start threshold value HTs2 for the comparison with the second heating temperature information of the second heating temperature sensor 90 b are used as heating start threshold values HTs. The first heating start threshold value HTs1 is a temperature value higher than the second heating start threshold value HTs2. Similarly, a first heating stop threshold value HTe1 for the comparison with the first heating temperature information and a second heating stop threshold value HTe2 for the comparison with the second heating temperature information are used as heating stop threshold values HTe. The first heating stop threshold value HTe1 is a temperature value higher than the second heating stop threshold value HTe2.

The heating device command section 112 controls the heating and the stopping of the heating by the heating device 18, by outputting a heating device command to a driver (not shown in the drawings) of the heating device 18, based on the comparison result of the heating determining section 110. A relay switch that switches between conduction and non-conduction of the heating wires 86, based on the heating device command, is used as this driver. The specific operation of the heating device 18 is described further below.

The heating control section 96 may be configured to allow heating or disallow heating based on the air flow rate of the heating device 18. In other words, the control device 20 can stop the heating performed by the heating device 18 by disallowing the heating performed by the heating device 18 when the air is not flowing at a flow rate greater than or equal to a prescribed flow rate.

The water electrolysis system 10 according to the present embodiment is basically configured as described above, and the following describes the operation thereof.

The following describes an example of the operation of the water electrolysis system 10 in a case where the air temperature has become high in summer or the like. In the water electrolysis system 10, as the surrounding temperature becomes higher, the temperature of the space 14 a in the housing 14 becomes higher. In addition to this, if the water electrolysis unit 12 is being driven, the space 14 a in the housing 14 is warmed by exhaust heat from the water electrolysis device 22 and the like.

The ventilation temperature sensor 88 detects the temperature above the water electrolysis device 22, where hot air is prone to collect in the space 14 a (causing a high temperature within the space 14 a). Most of the space 14 a is at a temperature lower than the temperature near the ventilation temperature sensor 88, and therefore, by the temperature detection by the ventilation temperature sensor 88, the water electrolysis system 10 can quickly sense a temperature change within the housing 14.

Here, the water electrolysis system 10 implements the normal ventilation control, under the control of the control device 20 (ventilation control section 94), to ventilate the inside of the housing 14. With the normal ventilation control, the second and third fans 74B and 74C of the ventilation device 16 are constantly rotating. At this time, the flow rate calculating section 100 calculates the calculated flow rate from the flow rate information of the flow rate sensor 92, and the ventilation content setting section 102 sets the rotational speed of the second and third fans 74B and 74C based on this calculated flow rate. The regular fan command section 104 then outputs the regular fan command with the set rotational speed, to cause the second and third fans 74B and 74C to rotate.

Due to the rotation of the second and third fans 74B and 74C, the air brought into the space 14 a from outside the housing 14 flows through the regular flow path 70 a. In other words, the air passes through the heating device 18 that is in a non-heating state, and thereafter flows around the control device 20 in the internal wall structure 72, and the air then flows around each device including the water electrolysis unit 12. Therefore, even when hydrogen leaks out from the water electrolysis unit 12, the water electrolysis system 10 can prevent the hydrogen from heading toward the control device 20 and discharge the hydrogen to the outside of the housing 14 (prevent explosion of the hydrogen).

During the normal ventilation control, when the ventilation temperature information of the ventilation temperature sensor 88 is less than or equal to the flow rate increase starting threshold value FTs, the control device 20 stops the rotation of the first and fourth fans 74A and 74D, and also sets the first and fourth fans 74A and 74D to the closed state using the cutoff device 80. In this way, by closing the first and fourth fans 74A and 74D with the cutoff device 80, the air in the space 14 a is prevented from escaping from the gaps in the first and fourth fans 74A and 74D.

Then, in a state where only the second and third fans 74B and 74C are rotating, the ventilation determining section 98 of the control device 20 acquires the ventilation temperature information of the ventilation temperature sensor 88 and makes a comparison between the ventilation temperature information and the flow rate increase starting threshold value FTs. As a result of this comparison, if the ventilation temperature information is less than or equal to the flow rate increase starting threshold value FTs, the state in which only the second and third fans 74B and 74C are rotating and the first and fourth fans 74A and 74D are rotationally stopped (and closed by the cutoff device 80) is maintained. Then, at time t1, when the ventilation determining section 98 determines that the ventilation temperature information has exceeded the flow rate increase starting threshold value FTs, switching is performed from the normal ventilation control to the forced air cooling control.

Specifically, when the forced air cooling control starts (time t1), the ventilation content setting section 102 first operates the cutoff device 80 via the cutoff device command section 108 to switch the first and fourth fans 74A and 74D from the closed state to the open state.

At time t2 that is slightly later than time t1, the ventilation content setting section 102 performs control to start rotating the first fan 74A before the fourth fan 74D rotates. Due to this, it is possible to increase the flow rate of the air in the space 14 a in a stepped manner. Upon starting to rotate, the first fan 74A has its rotational speed gradually increase toward the target rotational speed at a rotational speed increase rate causing a noise level that is difficult to hear. Furthermore, after the cutoff device 80 has entered the open state (time t2), the control device 20 performs control to temporarily increase the rotational speed of the second and third fans 74B and 74C. Owing to this, it is possible to prevent a decrease in the hydrogen explosion prevention capability due to a drop in the flow rate of the air in the space 14 a caused by the first and fourth fans 74A and 74D being in the open state.

When the rotational speeds of the first to third fans 74A to 74C have all reached the same command value (an upper limit value that takes the noise level into consideration) at time t3, the control device 20 starts rotation of the fourth fan 74D. Upon starting to rotate, the fourth fan 74D also has its rotational speed gradually increase toward the target rotational speed at a rotational speed increase rate causing a noise level that is difficult to hear. As a result, the first to fourth fans 74A to 74D of the ventilation device 16 all rotate, and the air having the target flow rate (ventilation air flow rate in the forced air cooling control) flows through the space 14 a at time t4. With this forced air cooling control, the first to fourth fans 74A to 74D rotate at the same rotational speed as each other, and the second and third fans 74B and 74C rotate at a higher rotational speed than during the normal ventilation control.

During the forced air cooling control, the air flowing into the housing 14 flows through both the regular flow path 70 a and the additional flow path 70 b, to experience heat exchange with the control device 20, the water electrolysis unit 12, and the like. This air has its temperature increased due to the water electrolysis device 22 and the like, but by causing a large amount of this air to flow due to the rotation of the first to fourth fans 74A to 74D, it is possible to sufficiently lower the temperature of the space 14 a. Therefore, when a certain amount of time has passed from starting of the forced air cooling control, the temperature of the upper portion in the housing 14 also drops and the ventilation temperature sensor 88 detects ventilation temperature information exhibiting a gradual decrease.

Here, during the forced air cooling control (during rotation of the first and fourth fans 74A, 74D), the ventilation determining section 98 makes a comparison between the ventilation temperature information of the ventilation temperature sensor 88 and the flow rate increase stopping threshold value FTe. This is aimed at measuring the stop timing of the forced air cooling control. As described above, the flow rate increase stopping threshold value FTe is a value lower than the flow rate increase starting threshold value FTs. In a case where the ventilation temperature information exceeds the flow rate increase stopping threshold value FTe, the ventilation determining section 98 continues the rotation of the first and fourth fans 74A and 74D.

Then, at time t5 that occurs a certain amount of time after the start of the forced air cooling control, the ventilation determining section 98 determines that the ventilation temperature information has become less than or equal to the flow rate increase stopping threshold value FTe. The ventilation content setting section 102 performs a process to stop the forced air cooling control, based on this determination. With this stopping process, first, the rotational speed of the fourth fan 74D is gradually reduced until the rotation is ultimately stopped. Furthermore, at time t5, the ventilation content setting section 102 ensures the flow rate needed to ventilate the housing 14 and prevent an explosion inside the housing 14, by performing control to temporarily increase the rotational speed of the second and third fans 74B and 74C.

At time t6 when the rotation of the fourth fan 74D stops, the ventilation content setting section 102 gradually reduces the rotational speed of the first fan 74A until ultimately stopping the rotation. At time t7 when the rotation of the first fan 74A stops, the ventilation content setting section 102 operates the cutoff device 80 to transition the first and fourth fans 74A and 74D from the open state to the closed state. In this way, the water electrolysis system 10 returns to the normal ventilation control where only the second and third fans 74B and 74C rotate to ventilate the inside of the housing 14.

The following describes an example of an operation performed by the water electrolysis system 10 in a case where the temperature has become low (less than or equal to the freezing point of water) in winter or the like, with reference to FIG. 6. In this case, in order to prevent freezing of the water electrolysis unit 12, the water electrolysis system 10 performs control to keep the temperature inside the housing 14 greater than or equal to a prescribed value (e.g., 0° C.)

Here, since the inside of the housing 14 is ventilated even when the surrounding temperature is low, the water electrolysis system 10, under the control of the control device 20 (ventilation control section 94), implements the normal ventilation control in which the second and third fans 74B and 74C are constantly rotating. The air flowing into the space 14 a due to the rotation of the second and third fans 74B and 74C flows through the regular flow path 70 a, and is guided to the ventilation outlet 64 through the region surrounding the water electrolysis unit 12 after passing through the heating device 18.

The water electrolysis system 10 then monitors the temperature of the air flowing through the regular flow path 70 a, using the first heating temperature sensor 90 a positioned near the downstream side of the heating device 18 and the second heating temperature sensor 90 b positioned near the upstream side of the water electrolysis device 22. The heating control section 96 of the control device 20 controls the heating device 18 based on the first heating temperature information and the second heating temperature information from the first and second heating temperature sensors 90 a and 90 b.

Specifically, in a state where the operation of the heating device 18 is stopped, the heating determining section 110 reads the first heating start threshold value HTs1 and the second heating start threshold value HTs2. The heating determining section 110 then implements a first comparison to compare the first heating temperature information to the first heating start threshold value HTs1 and, in parallel with this first comparison, implements a second comparison to compare the second heating temperature information to the second heating start threshold value HTs2. If the heating temperature information exceeds the respective heating start threshold value HTs in both the first and second comparisons, a determination is made to keep the heating device 18 in the operationally stopped state. If the heating temperature information is less than or equal to the heating start threshold value HTs in either of the first and second comparisons, a determination is made to start the operation of the heating device 18.

For example, at time t11 in FIG. 6, the heating determining section 110 determines that the first heating temperature information has become less than or equal to the first heating start threshold value HTs1. The heating device command section 112 outputs a command to perform driving of the heating device 18, based on the determination made by the heating determining section 110. In other words, by causing energization of (supplying power to) the heating wires 86 of the heating device 18, the water electrolysis system 10 heats the air passing through the cavity 84 a of the box 84. This heated air flows to the water electrolysis device 22 on the downstream side of the heating device 18, so that the surrounding temperature of the water electrolysis unit 12 increases and the water of the water electrolysis unit 12 is kept at a non-freezing temperature.

Furthermore, when the heating device 18 is in the heating state, the heating determining section 110 reads the first heating stop threshold value HTe1 and the second heating stop threshold value HTe2. The heating determining section 110 then implements a first comparison to compare the first heating temperature information to the first heating stop threshold value HTe1 and, in parallel with this first comparison, implements a second comparison to compare the second heating temperature information to the second heating stop threshold value HTe2. If the heating temperature information is less than or equal to respective the heating stop threshold value HTe in both the first and second comparisons, a determination is made to keep the heating device 18 in the heating state. If the heating temperature information exceeds the heating stop threshold value HTe in either of the first and second comparisons, a determination is made to stop the operation of the heating device 18.

For example, at time t12 in FIG. 6, the heating determining section 110 determines that the first heating temperature information has exceeded the first heating stop threshold value HTe1, which is higher than the first heating start threshold value HTs1. The heating device command section 112 stops the heating state caused by the heating device 18, based on the determination made by the heating determining section 110.

As a further example, at time t13, with the heating device 18 in the heating stopped state, the heating determining section 110 determines that the second heating temperature information has become less than or equal to the second heating start threshold value HTs2. Due to this, the heating device command section 112 starts the heating by the heating device 18. Then, at time t14, with the heating device 18 in the operating state, the heating determining section 110 determines that the second heating temperature information has exceeded the second heating stop threshold value HTe2. Due to this, the heating device command section 112 stops the heating by the heating device 18.

By comparing the temperature information of the first heating temperature sensor 90 a and the temperature information of the second heating temperature sensor 90 b to the threshold values as described above, the water electrolysis system 10 can cause the heating device 18 to appropriately operate even when there is temperature unevenness in the space 14 a in the housing 14. In this way, it is possible to reliably prevent freezing of the water electrolysis unit 12.

The water electrolysis system 10 may be configured to include one heating temperature sensor 90 in the regular flow path 70 a, and to control the operation of the heating device 18 based on this heating temperature information. Furthermore, the water electrolysis system 10 may be configured to start the heating by the heating device 18 when pieces of heating temperature information from a plurality of heating temperature sensors 90 are all less than or equal to respective heating start threshold values HTs, and to stop the heating by the heating device 18 when these pieces of information all exceed respective heating stop threshold values HTe.

The water electrolysis system 10 described above realizes the effects described below.

By including the ventilation temperature sensor 88, the heating temperature sensor 90, and the control device 20, the water electrolysis system 10 can appropriately control the operation of the ventilation device 16 and the heating device 18. For example, since the temperature in the housing 14 rises and hot air tends to gather in the top portion of the water electrolysis device 22 during the summer, the control device 20 can lower the temperature inside the housing 14 by increasing the ventilation air flow rate based on the ventilation temperature information of the ventilation temperature sensor 88. Furthermore, even when the temperature outside the housing 14 drops in winter, it is possible to avoid freezing of the water electrolysis unit 12 by using the heating device 18 to heat the air based on the heating temperature information of the heating temperature sensor 90 provided in the flow path 70 between the water electrolysis device 22 and the heating device 18. In other words, the water electrolysis system 10 can maintain a favorable operating environment for each device by suitably adjusting the temperature in the housing 14, even as the temperature outside the housing 14 changes throughout the year.

The water electrolysis system 10 can effectively cool the inside of the housing 14 as needed, by increasing the air flow rate of the ventilation device 16 when the ventilation temperature information, which is the temperature near the ventilation outlet 64, exceeds the flow rate increase starting threshold value FTs.

The water electrolysis system 10 can moderately cool the inside of the housing 14 and also prevent explosions by discharging the hydrogen from inside the housing 14, by causing the regular fans 76 of the ventilation device 16 to always rotate. Furthermore, it is possible to significantly cool the inside of the housing 14 because it is easy to increase the ventilation air flow rate by causing the additional fans 78 to rotate when the ventilation temperature information exceeds the flow rate increase starting threshold value FTs.

When rotation of the additional fans 78 starts, the water electrolysis system 10 first causes some of the plurality of additional fans 78 to rotate, and then causes the other of the plurality of additional fans 78 to rotate. Therefore, it is possible to increase the ventilation air flow rate in the space 14 a, while causing the air to flow smoothly in the housing 14. Similarly, it is possible to decrease the ventilation air flow rate in the space 14 a while causing the air to flow smoothly, also when the rotation of the additional fans 78 is stopped.

The water electrolysis system 10 includes the cutoff device 80 that closes the additional fans 78 when the additional fans 78 are in the rotationally stopped state. Therefore, the water electrolysis system 10 can prevent a drop in the ventilation air flow rate in the housing 14, caused by the air flowing out from the additional fans 78 due to rotation of the regular fans 76.

When the additional fans 78 transition from the closed state to the open state by action of the cutoff device 80, the control device 20 increases the rotational speed of the regular fans 76. Therefore, the water electrolysis system 10 can stably perform ventilation in the housing 14, by restricting a decrease in the ventilation air flow rate caused by air escaping from the space 14 a due to the state change of the cutoff device 80.

The water electrolysis system 10 can guide the air that has been heated by the operation of the heating device 18 in winter or the like to the water electrolysis unit 12, by passing the air being constantly blown by the regular fans 76 through the heating device 18 in the regular flow path 70 a. Furthermore, the water electrolysis system 10 can cool the inside of the housing 14 in a short time using air when the additional fans 78 are rotating, using the additional flow path 70 b that does not pass through the heating device 18.

The water electrolysis system 10 can reliably cause air to flow at a flow rate necessary for ventilation inside the housing 14, by changing the rotational speed of the regular fans 76 and the additional fans 78, based on the flow rate information detected by the flow rate sensor 92.

The control device 20 starts the heating by the heating device 18 when the heating device 18 is in the heating stopped state and the heating temperature information becomes less than or equal to the heating start threshold value HTs, and stops the heating by the heating device 18 when the heating device 18 is in the heating state and the heating temperature information has exceeded the heating stop threshold value HTe. Therefore, when the temperature of the regular flow path 70 a in which the heating temperature sensor 90 is provided has dropped, the heating device 18 can heat the air at an appropriate timing to prevent freezing of the water electrolysis unit 12.

The control device 20 controls the heating and non-heating by the heating device 18, based on any one of the first heating temperature information of the first heating temperature sensor 90 a and the second heating temperature information of the second heating temperature sensor 90 b. Therefore, even when there is temperature unevenness in the housing 14, it is possible to more reliably cause the heating device 18 to operate to thereby prevent freezing.

The water electrolysis system 10 includes the control device 20 provided on the upstream side of the water electrolysis device 22 in the flow path 70 and to the side of the water electrolysis device 22. Therefore, even if hydrogen leaks out from the water electrolysis device 22, the water electrolysis system 10 can prevent the hydrogen from heading toward the control device 20 and avoid accidents such as ignition of the hydrogen by the control device 20.

The present invention is not limited to the embodiments described above, and various modifications may be made without deviating from the scope of the present invention. For example, the rotational speed (number of rotations per unit time) of the plurality of fans 74 of the ventilation device 16 may differ between the fans, as long as a suitable air flow rate can be achieved. In this case, as an example, the rotational speed of each fan 74 is changed such that the fundamental frequency of the wind noise is dispersed. 

What is claimed is:
 1. A water electrolysis system comprising: a water electrolysis unit including a water electrolysis device configured to perform water electrolysis; a housing that includes therein a space through which air flows, and houses the water electrolysis unit in the space; a ventilation device configured to cause the air to flow inside the space; a heating device provided on an upstream side of the water electrolysis device in a flow path of the air, and configured to heat the air; a ventilation temperature sensor provided above the water electrolysis device in the space; a heating temperature sensor provided between the heating device and the water electrolysis device in the flow path; and a control device configured to control operation of the ventilation device based on ventilation temperature information detected by the ventilation temperature sensor, and also control operation of the heating device based on heating temperature information detected by the heating temperature sensor.
 2. The water electrolysis system according to claim 1, wherein the housing includes a ventilation outlet configured to allow the air to flow outside from the space therethrough, the ventilation temperature sensor is provided at a position near the ventilation outlet, and the control device includes a flow rate increase starting threshold value, and increases a flow rate of the air using the ventilation device when the ventilation temperature information changes from being less than or equal to the flow rate increase starting threshold value to exceeding the flow rate increase starting threshold value.
 3. The water electrolysis system according to claim 2, wherein the ventilation device includes a regular fan configured to always rotate to cause the air to flow, and an additional fan configured to rotate when the ventilation temperature information exceeds the flow rate increase starting threshold value to thereby increase the flow rate of the air.
 4. The water electrolysis system according to claim 3, wherein the additional fan of the ventilation device comprises a plurality of additional fans, when the additional fans start rotating, the control device causes part of the plurality of additional fans to rotate first, and then causes other part of the plurality of additional fans to rotate, and when rotation of the additional fans is being stopped, the control device first stops rotation of part of the plurality of additional fans, and then stops rotation of other part of the plurality of additional fans.
 5. The water electrolysis system according to claim 3, wherein the ventilation device includes a cutoff device configured to, with the additional fan in an operationally stopped state, close the additional fan.
 6. The water electrolysis system according to claim 5, wherein when the additional fan transitions from a closed state to an open state by the cutoff device, the control device increases a rotational speed of the regular fan.
 7. The water electrolysis system according to claim 3, wherein the flow path includes a regular flow path through which the air is caused to flow by the regular fan and an additional flow path through which the air is caused to flow by the additional fan, and the regular flow path passes through the heating device, but the additional flow path does not pass through the heating device.
 8. The water electrolysis system according to claim 3, further comprising: a flow rate sensor configured to detect the flow rate of the air at a position near the ventilation outlet, wherein the control device changes rotational speeds of the regular fan and the additional fan, based on flow rate information detected by the flow rate sensor.
 9. The water electrolysis system according to claim 1, wherein the control device includes a heating start threshold value and a heating stop threshold value that is higher than the heating start threshold value, the control device starts heating by the heating device when, with the heating device in a heating stopped state, the heating temperature information becomes less than or equal to the heating start threshold value, and the control device stops heating by the heating device when, with the heating device in a heating state, the heating temperature information has exceeded the heating stop threshold value.
 10. The water electrolysis system according to claim 9, wherein the heating temperature sensor includes a first heating temperature sensor provided at a position near a downstream side of the heating device and a second heating temperature sensor provided at a position near an upstream side of the water electrolysis device, and the control device controls heating and stopping of heating by the heating device, based on either one of the first heating temperature information of the first heating temperature sensor and the second heating temperature information of the second heating temperature sensor.
 11. The water electrolysis system according to claim 1, wherein the control device is provided on an upstream side of the water electrolysis device in the flow path, and to a side of the water electrolysis device. 